CJA Crank Arm Shortener

(2 customer reviews)


Brand: CJ Ackley Machine

The CJA Crank Arm Shortener (also known as a bicycle crank length adapter) offers different pedal positions to assist cyclists with limited knee or hip flexion, or simply with shorter legs.

This model uses adjustable cams to capture the side of the existing crank arm, making it suitable for a wide range of cranks widths, and curvature profiles.

Available in two different widths for different crank arms.

SKU: N/A Category: Tags: , , ,
Brand: CJ Ackley Machine Company


The CJA Crank Arm Shortener is an alternative design to the Orthopedal model.  The main advantage is compatibility with curved and wider cranks, but otherwise, installation, range of adjustment, and functionality are all comparable.

Currently only available as a pair.

CJA Crank Arm Shortener Features and Benefits

  • Manufactured in the USA from high-grade aluminum alloy into an attractive shape that easily bolts onto your existing bicycle crank.
  • Handcrafted stainless steel bolts provide strength and durability
  • Useful for cyclists with short inseams (under 80cm) who would benefit from turning a smaller radius to resolve or prevent knee pain.
  • Pivotal for cyclists with limited lower limb range of motion due to injury or surgery
  • Reduces stress on the knees and hips
  • May reduce pain or discomfort
  • NOTE: The use of this product will increase the stance width of the cyclist, equivalent to the width of the crank arm on each side.
  • Installs in 10 minutes

Model Choices

Narrow: this model fits on cranks arms with a width of 18mm – 29mm (3/4″ to 1 3/16″). These will typically be found on older model stationary indoor exercise bikes.  Available in Silver only.

Standard:this model fits on crank arms with a width of 23mm – 42mm (7/8″ to 1 5/8″). This is more common on newer bikes. Available in Black only.



  • Works well with curved crank arms as well as straight crank arms.
  • Standard 9/16″ pedal axle holes. Optional 1/2″ bolt available for older style exercise bikes using 1/2″ pedal axles.
  • Suitable for use on regular bicycles, e-bikes, and indoor exercise bikes such as the Peloton bike
  • 210 lb weight limit on upright bikes.
  • Do not stand on pedals continuously.

What’s in the Box?

  • Instructions,
  • Right & Left sides
  • Mounting hardware,
  • 1/4 Allen key
  • A small single-application Loctite tube.


  • Shortens crank arms by 24, 41, 58 and 75mm  (i.e 4 pedal mounting holes)
  • Standard 9/16″ pedal axle holes
  • Optional 1/2″ pedal bolts
  • Adjustable cams to fit a variety of crankarm widths from 23 to 42mm

Installation Tips

  • Remember, left marked shortener goes on left side crank arm, and right marked shortener goes on right crank arm.
  • If you are installing these and the bolt does not tighten the shortener onto the crank arm firmly, you may have a thin crankarm.  To take up the play, use one or more pedal washers over the bushing that goes into the crank peal hole from the inside.  You can get them from a bike shop, or online in our store here.

What Our Customers Are Saying

We just got our fit kit in for my e-bike. I am 5ft and have a very short inseam. With the seat down to fit me, the pedals were so high and uncomfortable and didn’t feel safe. My husband just installed them! These are perfect and I’m so grateful. Thank you for making it easier for me to be comfortable and safe while riding. ❤️

-Linda Evins Mappin

Additional information

Weight0.9 lbs
Dimensions8.5 × 5.3 × 1.6 in

Narrow, Standard


Silver, Black

2 reviews for CJA Crank Arm Shortener

5.0 Rating
1-2 of 2 reviews
  1. Verified reviewVerified review - view originalExternal link

    Great for aluminum crank design

    (0) (0)
  2. (1) (0)
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